1. Field of the Invention
This invention relates to an improved process for the production of glyoxylic acid by the use of a combination of enzymatic and non-enzymatic catalyzed oxidation of glycolic acid. More specifically, the present invention relates to the use of glycolate oxidase and a non-enzymatic catalyst for the decomposition of hydrogen peroxide.
2. Description of the Related Art
Glycolate oxidase, an enzyme commonly found in leafy green plants and mammalian cells, catalyzes the oxidation of glycolic acid to glyoxylic acid, with the concomitant production of hydrogen peroxide. N. E. Tolbert et al., J. Biol. Chem., Vol. 181, 905-914 (1949) first reported an enzyme, extracted from tobacco leaves, which catalyzed the oxidation of glycolic acid to formic acid and CO.sub.2 via the intermediate formation of glyoxylic acid. The addition of certain compounds, such as ethylene diamine, limited the further oxidation of the intermediate glyoxylic acid. The oxidations were carried out at a pH of about 8, typically using glycolic acid concentrations of about 3-40 mM (millimolar). The optimum pH for the glycolate oxidation was reported to be 8.9. Oxalic acid (100 mM) was reported to inhibit the catalytic action of the glycolate oxidase. Similarly, K. E. Richardson and N. E. Tolbert, J. Biol. Chem., Vol. 236, 1280-1284 (1961) showed that buffers containing tris(hydroxymethyl)aminomethane inhibited the formation of oxalic acid in the glycolate oxidase catalyzed oxidation of glycolic acid. C. O. Clagett, N. E. Tolbert and R. H. Burris, J. Biol. Chem., Vol. 178, 977-987 (1949) reported that the optimum pH for the glycolate oxidase catalyzed oxidation of glycolic acid with oxygen was about 7.8-8.6, and the optimum temperature was 35.degree.-40.degree. C.
I. Zelitch and S. Ochoa, J. Biol. Chem., Vol. 201, 707-718 (1953), and J. C. Robinson et al., J. Biol. Chem., Vol. 237, 2001-2009 (1962), reported that the formation of formic acid and CO.sub.2 in the spinach glycolate oxidase-catalyzed oxidation of glycolic acid resulted from the non-enzymatic reaction of H.sub.2 O.sub.2 with glyoxylic acid. They observed that addition of catalase, an enzyme that catalyzes the decomposition of H.sub.2 O.sub.2, greatly improved the yields of glyoxylic acid by suppressing the formation of formic acid and CO.sub.2. The addition of FMN (flavin mononucleotide) was also found to increase the stability of the glycolate oxidase.
N. A. Frigerio and H. A. Harbury, J. Biol. Chem., Vol. 231, 135-157 (1958) have reported on the preparation and properties of glycolic acid oxidase isolated from spinach. The purified enzyme was found to be very unstable in solution; this instability was ascribed to the relatively weak binding of flavin mononucleotide (FMN) to the enzyme active site, and to the dissociation of enzymatically active tetramers and/or octamers of the enzyme to enzymatically-inactive monomers and dimers, which irreversibly aggregate and precipitate. The addition of FMN (flavin mononucleotide) to solutions of the enzyme greatly increased its stability, and high protein concentrations or high ionic strength maintained the enzyme as octamers or tetramers.
There are numerous other references to the oxidation of glycolic acid catalyzed by glycolic acid oxidase, for example:
Isolation of the Enzyme
(usually includes an assay method):
I. Zelitch in Methods of Enzymology, Vol. 1, Academic Press, New York, 1955, p. 528-532, from spinach and tobacco leaves.
M. Nishimura et al., Arch. Biochem. Biophys., Vol. 222, 397-402 (1983), from pumpkin cotyledons.
H. Asker and D. Davies, Biochim. Biophys. Acta, Vol. 761, 103-108 (1983), from rat liver.
M. J. Emes and K. H. Erismann, Int. J. Biochem., Vol 16, 1373-1378 (1984), from Lemna Minor L.
Structure of the enzyme:
E. Cederlund et al., Eur. J. Biochem., Vol. 173, 523-530 (1988).
Y. Lindquist and C. Branden, J. Biol. Chem., Vol. 264, 3624-3628, (1989).